The invention relates to a method for initializing an anti-theft system for a motor vehicle and, in particular, for initializing a remote-controlled central locking system.
A prior art anti-theft system described in German patent DE 43 02 550 C2 has a portable transmitter which transmits code signals to a receiver in the motor vehicle in order to remotely control the central locking system. With that system, the code signals are changed with respect to the previous transmission each time a transmission is made (rolling code).
When that anti-theft system is initialized, the transmitters and receivers are initially placed in an initialization state by inputting a special signal via a diagnostic interface or by activating the ignition lock in an unusual way. Then, the receiver must receive a code signal of a previously authorized transmitter before it is possible for the initialization to be carried out.
Such an anti-theft system can be initialized after a battery change only if the last valid code signal is still stored in the transmitter. A complex memory is necessary for that purpose, which inevitably requires more energy. If a simple memory, such as the already available RAM, is used, then the last valid code signal is no longer retained after a battery change. As a result, it is not possible to transmit a valid code signal after a battery change, and the anti-theft system cannot be initialized.
In such an anti-theft system there is, moreover, the risk that during the initialization the transmitter may be too far away from the receiver. The receiver then does not receive the start value generated in the key. As a result, while the transmitter is initialized, the receiver is not. As a result, the transmitter can no longer control the central locking system, since the two are no longer xe2x80x9ccompatible with one another.xe2x80x9d
German patent DE 44 11 450 C1 describes a system in which one-way function values for protecting the code are stored at the vehicle end. Reading out the values does not make it possible to manufacture a duplicate key without authorization and thus perform unauthorized initialization.
German patent DE 195 16 992 C1 describes an anti-theft system in which a request signal is transmitted from the motor vehicle to a transponder. The request signal contains a memory address at which the transponder reads out a corresponding code signal in its memory and transmits it back to the motor vehicle.
A further anti-theft system is described in German published non-prosecuted patent application DE 43 25 221 A1. There, a memory standby state is activated by means of a coding of a key, which coding has already been stored. After the key has been identified, the anti-theft system activates a mode by means of which the coding of a further key is stored in the anti-theft system.
It is accordingly an object of the invention to provide a method of initializing an anti-theft system of a motor vehicle, which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type and wherein the anti-theft system is of simple construction and allows a user easy and reliable initialization.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of initializing an anti-theft system of a motor vehicle, wherein the anti-theft system includes:
a key with a remote control unit for selectively locking and unlocking a central locking system and with a transponder for releasing an immobilizer;
a receiver disposed in the motor vehicle and adapted to receive and evaluate signals of the remote control unit; and
a transceiver unit on a lock of the motor vehicle, the transceiver unit being adapted to transmit a request signal to the transponder, to receive a coded response signal from the transponder, and to check the response signal for authorization;
the method which comprises the following steps:
placing the receiver and the transceiver unit into an initialization state;
transmitting a request signal to the transponder;
transmitting a response signal to the transceiver unit;
checking the response signal for its authorization by comparing an item of code information contained in the response signal with an expected item of reference code information;
if the response signal is determined to be authorized in the checking step, transmitting a coded start value to the key and storing the start value in a memory of the key; and
forwarding the start value from the key to the receiver.
In other words, the objects of the invention are satisfied with the following sequence: First, a vehicle-end receiver and a transceiver unit in the motor vehicle are placed in an initialization state. Then, the transceiver unit transmits a request signal to a transponder on a key which responds to it with a response signal. The authorization of the response signal is checked in the transceiver unit. If the response signal is authorized, a start signal is transmitted to the key and stored there. In addition, the start signal is forwarded from the key to the receiver and likewise stored there.
During the process, the key is located in the direct vicinity of the receiver. This largely ensures.that the signals transmitted during the initialization reach both the key and the receiver.
In accordance with an added feature of the invention, the start value is stored in a memory of the receiver, and a coded remote-control rolling code signal is generated with the start value as an initial value of the rolling code.
In accordance with another feature of the invention, a successful initialization is indicated to the user with a display unit, such as by visual and/or audible display.
In accordance with an additional feature of the invention, the signals between the transponder and the transceiver unit are transmitted in the form of inductive energy, optical energy, and/or data signals. The signals from the remote control unit to the receiver are transmitted as optical and/or high-frequency data signals.
In accordance with a further feature of the invention, the placing step comprises activating the key in the lock in a defined unusual manner within a predefined time period.
In accordance with an alternative feature of the invention, an external device is connected to a diagnostics interface of the motor vehicle and an initialization signal is transmitted that places the receiver and the transceiver unit in the initialization state.
With the above and other objects in view there is also provided, in accordance with the invention, a method of initializing the anti-theft system which comprises the following steps:
placing the receiver and the transceiver unit into an initialization state;
transmitting a request signal to the transponder;
calculating a response signal and returning the response signal to the transceiver unit and/or generating a start value in the transponder;
checking the response signal for its authorization by comparing an item of code information contained in the response signal with an expected and stored item of reference code information;
transmitting a coded start value to the key or requesting the transponder to use the start value if the response signal has been detected as authorized; and
forwarding the start value from the key to the receiver or requesting to accept the previously calculated start value.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for initializing an anti-theft system for a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.